A transfusion medicine physician in Tennessee wonders what other institutions use as indications for selecting donor RBC units that have been tested for hemoglobin S and found to be 'sickle-negative'. At her institution the indication for selecting sickle-negative RBCs is for pediatric patients undergoing ECMO.

Editor's note: The earlier e-Network Forum discussion Is it a safe practice to transfuse sickle trait donor RBC units to patients with sickle cell disease? is germane to the current discussion.

The following comments have been received.

ADDENDA Sept. 1, 2005

1. Martin Maley, Section Head Hospital Reference Red Cell Immunohaematology Department of the National Blood Service, Newcastle-upon-Tyne, UK (attribution used with permission) reports that in the UK NBS (Newcastle Centre) all red cell units destined for pediatric use (whether for intrauterine transfusion, exchange transfusion, or top-up transfusion) must be sickle hemoglobin negative. The latter of these (top-up) is more a requirement of their computer system than based on any scientific basis. Also, they recommend that pediatric patients undergoing ECMO, and any patient with sickle cell disease undergoing "exchange transfusion" should receive units that are sickle hemoglobin negative.

2. A colleague in a Rocky Mountain state is aware that that RBC components collected from donors with sickle cell trait frequently occlude WBC-reduction filters. She wonders if it would be reasonable to assume that the successful filtration by a leukocyte reduction filter of an RBC unit would imply that the unit had been "screened" for sickle trait.

Editor's note: Several investigators have reported that RBC components collected from donors with sickle cell trait occlude WBC-reduction filters. However, some sickle trait RBC units will pass thru the leukocyte reduction filters without incident. Thus, leukocyte reduction would probably NOT be a reliable method for screening donors for sickle hemoglobin. However, it would seem reasonable to test an RBC unit that failed filtration for the presence of sickle hemoglobin, to see if that was the reason for the failure.

See:

• Beard MJ et al, Variables determining blockage of WBC-depleting filters by Hb sickle cell trait donations. Transfusion. 2004 Mar;44(3):422-30.
• Stroncek DF et al. Sickle Hb polymerization in RBC components from donors with sickle cell trait prevents effective WBC reduction by filtration. Transfusion. 2002 Nov;42(11):1466-72.
• Schuetz AN et al. Leukoreduction filtration of blood with sickle cell trait. Transfus Med Rev. 2004 Jul;18(3):168-76.
• Stroncek DF et al. Increasing hemoglobin oxygen saturation levels in sickle trait donor whole blood prevents hemoglobin S polymerization and allows effective white blood cell reduction by filtration. Transfusion. 2004 Sep;44(9):1293-9.
• Byrne KM et al. Increasing oxygen tension improves filtration of sickle trait donor blood. Br J Haematol. 2003 Aug;122(4):678-81.

ADDENDA Sept. 2, 2005

3. A medical technologist in San Diego reports that when she was a supervisor at a children's hospital in Southern California, she and her staff wondered if it would be reasonable to discontinue screening RBC units for sickle hemoglobin prior to use in ECMO, if the RBC units successfully flowed through a leukocyte reduction filter. She acknowledges that soon after the wondering began they screened a leukoreduced RBC unit for sickle hemoglobin, and the unit screened positive (and then confirmed positive). Thus, in her personal experience it is possible for a sickle trait RBC unit to successfully pass through a leukoreduction filter.

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator